Possibly consider using a shorter maxLifetime value - hikari connection pool spring boot

Question

After starting my SpringBoot application, getting an exception on few minutes of the server startup. Did not use any HikariPool Configuration externally, Spring Boot is using HikariPool by default This is the error I am getting in the console:

2020-02-20 03:16:23 - HikariPool-4 - Failed to validate connection 
com.mysql.cj.jdbc.ConnectionImpl@4c4180c8 (No operations allowed after connection closed.). 
Possibly consider using a shorter maxLifetime value.
2020-02-20 03:16:28 - HikariPool-4 - Failed to validate connection 
com.mysql.cj.jdbc.ConnectionImpl@679c2f50 (No operations allowed after connection closed.). 
Possibly consider using a shorter maxLifetime value.
2020-02-20 03:16:33 - HikariPool-4 - Failed to validate connection 
com.mysql.cj.jdbc.ConnectionImpl@16083061 (No operations allowed after connection closed.). 
Possibly consider using a shorter maxLifetime value.
2020-02-20 03:16:38 - HikariPool-4 - Failed to validate connection 
com.mysql.cj.jdbc.ConnectionImpl@4fcaf421 (No operations allowed after connection closed.). 
Possibly consider using a shorter maxLifetime value.
2020-02-20 03:16:43 - HikariPool-4 - Failed to validate connection 
com.mysql.cj.jdbc.ConnectionImpl@33df5d54 (No operations allowed after connection closed.). 
Possibly consider using a shorter maxLifetime value.
2020-02-20 03:16:48 - HikariPool-4 - Failed to validate connection 
com.mysql.cj.jdbc.ConnectionImpl@373d288c (No operations allowed after connection closed.). 
Possibly consider using a shorter maxLifetime value.
2020-02-20 03:16:48 - SQL Error: 0, SQLState: 08003
2020-02-20 03:16:48 - HikariPool-4 - Connection is not available, request timed out after 
30156ms.
2020-02-20 03:16:48 - No operations allowed after connection closed.
2020-02-20 03:16:48 - Servlet.service() for servlet [dispatcherServlet] in context with path 
[] threw exception [Request processing failed; nested exception is 
org.springframework.dao.DataAccessResourceFailureException: Unable to acquire JDBC 
Connection; nested exception is org.hibernate.exception.JDBCConnectionException: Unable to 
acquire JDBC Connection] with root cause

Answer 1

The problem is that the default value of the spring.datasource.hikari.maxLifetime (30 minutes - https://github.com/brettwooldridge/HikariCP#configuration-knobs-baby) is higher than the database's "wait_timeout" (10 minutes in my case).
So you have two options, either decrease the hikari.maxLifetime below 10 minutes, or increase the database's "wait_timeout" property.